For extension springs, you’ll need to know the length of the spring, the weight that it’s intended to hold and the outside diameter.
It is common that most residential garage doors are either seven or eight feet tall. Seven-foot doors usually use a 25-inch spring, and eight-foot doors use a 27-inch spring. However, because you don’t want to end up with the wrong spring because you are guessing, it is vital you measure the above components.
Extension Spring Length
If you don’t have a loose spring to measure, you can measure the extension spring in use by doing the following. First, make sure your garage door is closed. Unplug your garage door motor unit from the power source, and release the garage door itself by pulling on the brightly-colored release cord hanging down towards the front of the door.
Then, lift your garage door manually and carefully, you may need help. If only one spring is broken, lift from the broken spring side, otherwise, lift from the middle.
Once the door is open, clamp a vice grip inside the track beneath the wheel, just under the bottom of the garage door. This will keep your garage door from closing.
Then, hop up on a ladder and measure the overall and body length of the spring with a tape measure.
You can weigh your garage door with a regular mechanical bathroom scale. Center the scale in front of your closed garage door, making sure the garage door is disconnected from the opener after pulling on the release cord. Then, lift the door slightly and carefully, as it may be heavy, and slide the scale underneath. Let the door down slowly, and record the weight.
The Wire Diameter
We recommend that you measure the wire diameter in two different spots using a micrometer and take the average. This will allow your reading to be more accurate so that you are not purchasing the wrong spring.
Measure the outside diameter
When possible, you should measure the outside diameter in the middle of the spring because the end coils tend to run large.